No one asked this question... How big is your tank titoav15.
Also, if you don't have a QT tank, and you want to treat him.. you have no other alternative to GETTING a QT tank. Doing Hypo in the main tank, could kill other things in the tank as well. And dosing things like copper that would kill the ich parasite, would kill off your live rock, and any inverts you have in the tank. It really is not worth the hassle. Unless the rest of your tank, compared to your tang, is completely expendable, i would not even think about treating the ich ridden fish in your main tank.
And again i reiterate, how big is your tank.